The present invention relates generally to agricultural machinery such as harvesting machines and, more particularly to such a machine including a conveying device having conveying rollers with a metal foreign body detection device mounted in front of a chopper mechanism. The detection device controls rapid stopping of the conveying rollers whenever a foreign body is detected in a foreign body detection region of the conveying device, before the foreign body reaches the chopper mechanism.
A device of this kind is known from German Patent 4 129 113 A1. Whenever the conveying rollers are stopped because of detection of a foreign body, it is necessary to remove the foreign body from the conveying region so that the chopper mechanism is not encumbered by it. In some cases the foreign body leaves the conveying zone without further action through a gap between two conveying rollers arranged one behind the other. Often, however, the conveying direction must be reversed so that the foreign body can be removed from in front of the first conveying rollers or so that the foreign body is caused to drop out. Sometimes during reversed conveying the foreign body is picked up and entrained by the upper ribbed conveying roller, which generally is a pressure roller. Upon return to forward rotation the foreign body drops into the conveying path, that is, directly in front of the chopper and into the chopper mechanism. Also the foreign body frequently can be found only after long searching because the region of detection of the detection device is spatially extensive. Moreover, the rapid stop leaves a different path of conveying, depending upon the speed of conveying at the moment of switching. This makes it even more difficult to locate the foreign body. The sensitivity and filter properties of the detection device are influenced as a function of conveying speed signals and the gap width between the pressure roller and conveying drive roller. Thus, foreign bodies are detected from a critical size onward.
Also it is known from German Patent 4 301 611 A1 that several magnetic pole regions and detector coils can be arranged in the direction of conveying and transversely to the direction of conveying. As a result, various wanted signals are picked up in different regions of the path of conveying and hence extensive compensation of interference signals, which arise due to magnetic field-active structures, particularly transverse ribs, on the conveying rollers occurs.
It is an object of the invention to overcome one or more of the deficiencies described above.
It is another object to facilitate the removal of detected foreign bodies from the conveyor of an agricultural machine; and/or to improve the location for such removal.